This invention relates to a window for a motor vehicle. In particular, this invention relates to an improved polycarbonate window for a motor vehicle.
Motor vehicle windows, by and large, have heretofore been made from glass. It would be desirable to manufacture motor vehicle windows from a polycarbonate material, which is much lighter than glass. While use of polycarbonate plastic material has been acceptable for certain applications, such as for commercial bus windows, its lack of durability has precluded polycarbonate material from widespread use in passenger cars. In particular, conventional polycarbonate plastic material is subject to scuffing and marring during manufacture and at point of use. In addition, the desired stiffness could only be achieved with undesirably thick polycarbonate windows. Any attempt to reinforce the polycarbonate material has resulted in commercially unacceptable hazing or reduction in the transparency of the window. While Federal Motor Vehicle Safety Standard (FMVSS) 205 requires simply that vehicle windows to have at least 70% transmittance of visible light, the type of hazing that would result from conventional reinforcements would be aesthetically unappealing.
The disadvantages of the prior art may be overcome by providing a window for a motor vehicle comprising transparent polycarbonate plastic material and reinforcement particles dispersed within the polycarbonate material. The reinforcement particles comprise less than 10% of a total volume of the window. At least 50% of the reinforcement particles have a thickness of less than 10 nanometers. The reinforcement particles are selected and configured such that the window has a transmittance of visible light which is at least 95% of the transmittance of visible light that would exist through the window in the absence of the reinforcement particles.
It is a further object of the present invention to provide a window comprising a transparent thermoplastic material selected from the group consisting of polycarbonate and acrylic, and reinforcement particles dispersed within the thermoplastic material. The reinforcement particles comprise less than 10% of a total volume of the window. At least 50% of the reinforcement particles have a thickness of less than 10 nanometers. The reinforcement particles are selected and configured such that the window has a transmittance of visible light which is at least 95% of the transmittance of visible that would exist through the window in the absence of the reinforcement particles.
Because the nanoparticles are smaller than the wavelength of visible light, they are individually invisible to the naked eye. As a result, the nanoparticles can be impregnated into the polycarbonate or acrylic at loadings of preferably less than 10% by volume of the total volume of the window, and with particle sizes of preferably less than 10 nanometers in average thickness, without any appreciable decrease in transparency. In addition, the stiffness and scratch resistance of the window is greatly improved. Specifically, the stiffness can be improved by a factor of 1.5-4.0xc3x97 in comparison with unreinforced parts. In addition, scuff or mar resistance can also be improved by a factor of between about 1.4-4.0xc3x97. In addition, impact resistance can be improved or maintained while reducing the window""s thickness.